/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.core;

import javax.servlet.DispatcherType;
import javax.servlet.Servlet;
import javax.servlet.ServletRequest;

import org.apache.catalina.Globals;
import org.apache.catalina.Wrapper;
import org.apache.catalina.connector.Request;
import org.apache.tomcat.util.descriptor.web.FilterMap;

/**
 * Factory for the creation and caching of Filters and creation of Filter Chains.
 *
 * @author Greg Murray
 * @author Remy Maucherat
 */
public final class ApplicationFilterFactory {

    private ApplicationFilterFactory() {
        // Prevent instance creation. This is a utility class.
    }


    /**
     * Construct a FilterChain implementation that will wrap the execution of the specified servlet instance.
     *
     * @param request The servlet request we are processing
     * @param wrapper The wrapper managing the servlet instance
     * @param servlet The servlet instance to be wrapped
     *
     * @return The configured FilterChain instance or null if none is to be executed.
     */
    public static ApplicationFilterChain createFilterChain(ServletRequest request, Wrapper wrapper, Servlet servlet) {

        // If there is no servlet to execute, return null
        if (servlet == null) {
            return null;
        }

        // Create and initialize a filter chain object
        ApplicationFilterChain filterChain = null;
        if (request instanceof Request) {
            Request req = (Request) request;
            if (Globals.IS_SECURITY_ENABLED) {
                // Security: Do not recycle
                filterChain = new ApplicationFilterChain();
            } else {
                filterChain = (ApplicationFilterChain) req.getFilterChain();
                if (filterChain == null) {
                    filterChain = new ApplicationFilterChain();
                    req.setFilterChain(filterChain);
                }
            }
        } else {
            // Request dispatcher in use
            filterChain = new ApplicationFilterChain();
        }

        filterChain.setServlet(servlet);
        filterChain.setServletSupportsAsync(wrapper.isAsyncSupported());

        // Acquire the filter mappings for this Context
        StandardContext context = (StandardContext) wrapper.getParent();
        FilterMap filterMaps[] = context.findFilterMaps();

        // If there are no filter mappings, we are done
        if ((filterMaps == null) || (filterMaps.length == 0)) {
            return filterChain;
        }

        // Acquire the information we will need to match filter mappings
        DispatcherType dispatcher = (DispatcherType) request.getAttribute(Globals.DISPATCHER_TYPE_ATTR);

        String requestPath = null;
        Object attribute = request.getAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR);
        if (attribute != null) {
            requestPath = attribute.toString();
        }

        String servletName = wrapper.getName();

        // Add the relevant path-mapped filters to this filter chain
        for (FilterMap filterMap : filterMaps) {
            if (!matchDispatcher(filterMap, dispatcher)) {
                continue;
            }
            if (!matchFiltersURL(filterMap, requestPath)) {
                continue;
            }
            ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context
                    .findFilterConfig(filterMap.getFilterName());
            if (filterConfig == null) {
                // FIXME - log configuration problem
                continue;
            }
            filterChain.addFilter(filterConfig);
        }

        // Add filters that match on servlet name second
        for (FilterMap filterMap : filterMaps) {
            if (!matchDispatcher(filterMap, dispatcher)) {
                continue;
            }
            if (!matchFiltersServlet(filterMap, servletName)) {
                continue;
            }
            ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context
                    .findFilterConfig(filterMap.getFilterName());
            if (filterConfig == null) {
                // FIXME - log configuration problem
                continue;
            }
            filterChain.addFilter(filterConfig);
        }

        // Return the completed filter chain
        return filterChain;
    }


    // -------------------------------------------------------- Private Methods


    /**
     * Return <code>true</code> if the context-relative request path matches the requirements of the specified filter
     * mapping; otherwise, return <code>false</code>.
     *
     * @param filterMap   Filter mapping being checked
     * @param requestPath Context-relative request path of this request
     */
    private static boolean matchFiltersURL(FilterMap filterMap, String requestPath) {

        // Check the specific "*" special URL pattern, which also matches
        // named dispatches
        if (filterMap.getMatchAllUrlPatterns()) {
            return true;
        }

        if (requestPath == null) {
            return false;
        }

        // Match on context relative request path
        String[] testPaths = filterMap.getURLPatterns();

        for (String testPath : testPaths) {
            if (matchFiltersURL(testPath, requestPath)) {
                return true;
            }
        }

        // No match
        return false;

    }


    /**
     * Return <code>true</code> if the context-relative request path matches the requirements of the specified filter
     * mapping; otherwise, return <code>false</code>.
     *
     * @param testPath    URL mapping being checked
     * @param requestPath Context-relative request path of this request
     */
    private static boolean matchFiltersURL(String testPath, String requestPath) {

        if (testPath == null) {
            return false;
        }

        // Case 1 - Exact Match
        if (testPath.equals(requestPath)) {
            return true;
        }

        // Case 2 - Path Match ("/.../*")
        if (testPath.equals("/*")) {
            return true;
        }
        if (testPath.endsWith("/*")) {
            if (testPath.regionMatches(0, requestPath, 0, testPath.length() - 2)) {
                if (requestPath.length() == (testPath.length() - 2)) {
                    return true;
                } else if ('/' == requestPath.charAt(testPath.length() - 2)) {
                    return true;
                }
            }
            return false;
        }

        // Case 3 - Extension Match
        if (testPath.startsWith("*.")) {
            int slash = requestPath.lastIndexOf('/');
            int period = requestPath.lastIndexOf('.');
            if ((slash >= 0) && (period > slash) && (period != requestPath.length() - 1) &&
                    ((requestPath.length() - period) == (testPath.length() - 1))) {
                return testPath.regionMatches(2, requestPath, period + 1, testPath.length() - 2);
            }
        }

        // Case 4 - "Default" Match
        return false; // NOTE - Not relevant for selecting filters

    }


    /**
     * Return <code>true</code> if the specified servlet name matches the requirements of the specified filter mapping;
     * otherwise return <code>false</code>.
     *
     * @param filterMap   Filter mapping being checked
     * @param servletName Servlet name being checked
     */
    private static boolean matchFiltersServlet(FilterMap filterMap, String servletName) {

        if (servletName == null) {
            return false;
        }
        // Check the specific "*" special servlet name
        else if (filterMap.getMatchAllServletNames()) {
            return true;
        } else {
            String[] servletNames = filterMap.getServletNames();
            for (String name : servletNames) {
                if (servletName.equals(name)) {
                    return true;
                }
            }
            return false;
        }

    }


    /**
     * Convenience method which returns true if the dispatcher type matches the dispatcher types specified in the
     * FilterMap
     */
    private static boolean matchDispatcher(FilterMap filterMap, DispatcherType type) {
        switch (type) {
            case FORWARD:
                if ((filterMap.getDispatcherMapping() & FilterMap.FORWARD) != 0) {
                    return true;
                }
                break;
            case INCLUDE:
                if ((filterMap.getDispatcherMapping() & FilterMap.INCLUDE) != 0) {
                    return true;
                }
                break;
            case REQUEST:
                if ((filterMap.getDispatcherMapping() & FilterMap.REQUEST) != 0) {
                    return true;
                }
                break;
            case ERROR:
                if ((filterMap.getDispatcherMapping() & FilterMap.ERROR) != 0) {
                    return true;
                }
                break;
            case ASYNC:
                if ((filterMap.getDispatcherMapping() & FilterMap.ASYNC) != 0) {
                    return true;
                }
                break;
        }
        return false;
    }
}
